A REVIEW OF EARLY PERMIAN (300–270 MA) MAGMATISM IN EASTERN KAZAKHSTAN AND IMPLICATIONS FOR PLATE TECTONICS AND PLUME INTERPLAY

S V Khromykh,P D Kotler,N N Kruk,A E Izokh

doi:10.5800/gt-2019-10-1-0405

Abstract

The history of the Central Asian Orogenic Belt (CAOB) was marked by several major events of magmatism which produced large volumes of volcanic and intrusive (mafic-ultramafic and granitic) rocks within a relatively short time span (30–40 Ma) over a vast area. The magmatic activity postdated the orogenic stages of accretionary-collisional belts in Central Asia and likely resulted from the impact of mantle plumes that formed Large Igneous Provinces (LIPs). The formation of the Tarim–South Mongolia LIP at 300–270 Ma is the best known among the major Permian events of basaltic and granitic magmatism. Early Permian igneous rocks (volcanic, subvolcanic and intrusive suites that vary from ultramafic to felsic compositions) of the same age range (300 to 270 Ma) have been recently found also in Eastern Kazakhstan, within the late Paleozoic Altai collisional system. The compositions and ages of the rocks suggest that the Eastern Kazakhstan magmatism was the northward expansion of the Tarim LIP. The spread of the Tarim LIP was apparently facilitated by lithospheric extension after the Siberia-Kazakhstan collision. The extension led to rheological weakening of the lithosphere whereby deep mantle melts could penetrate to shallower depths. The early Permian history of Eastern Kazakhstan was controlled by the interplay of plate tectonic and plume processes: plate-tectonic accretion and collision formed the structural framework, and the Tarim mantle plume was a heat source maintaining voluminous magma generation.

Highlights

The Central Asian Orogenic Belt (CAOB) is the lar‐ gest accretionary structure in the Earth’s history, known as Altaids [Şengör et al, 1993], formed by clo‐ sure of the Paleoasian Ocean
From the viewpoints of plate tectonics, the post‐orogenic magmatism is caused by post‐orogenic lithospheric extension as a result of its delamination [Xiao et al, 2008; Xiao, Santosh, 2014; Konopelko et al, 2018] or results from active transten‐ sional strike‐slip tectonics accompanied by upwelling of the asthenosphere [Seltmann et al, 2011; Wang et al, 2014] or breaking of subducted oceanic plate [Konopelko et al, 2017]
The alternative viewpoint for large‐scale magmatism in accretionary‐ collision systems is the impact of mantle plumes

Summary

INTRODUCTION

The Central Asian Orogenic Belt (CAOB) is the lar‐ gest accretionary structure in the Earth’s history, known as Altaids [Şengör et al, 1993], formed by clo‐ sure of the Paleoasian Ocean. The plume activity leading to the formation of Large Igne‐ ous Provinces (LIPs) [Ernst et al, 2005; Bryan, Ernst, 2008; Ernst, 2014] can account for a number of Paleo‐ zoic magmatic events in CAOB: (1) early Paleozoic, with a late Cambrian – early Ordovician LIP in the Altai, Sayan and Western Mongolia regions [Izokh et al, 2010; Dobretsov, 2011; Vladimirov et al, 2013]; (2) middle Paleozoic, with a Devonian LIP in the Minusa basin and the Vilyui rift in East Siberia [Vorontsov et al, 2013; Kiselev et al, 2014]; and (3) late Paleozoic, with Permian LIPs in Central Asia. As con‐ firmed by recent studies, the Tarim LIP spreads over the regions of South Mongolia [Kozlovsky et al, 2015], Chinese Altai [Zhang et al, 2014], North‐Western Xin‐ jiang [Pirajno et al, 2011; Gao et al, 2014], and Tien Shan [Seltmann et al, 2011], as well as into Eastern Ka‐ zakhstan

LATE PALEOZOIC ALTAI ACCRETIONARY‐COLLISIONAL

10. ACKNOWLEDGEMENTS

11. REFERENCES